Micropayment schemes protecting customers’ identity privacy are proposed recently. Those proposed micropayment schemes only deal with payments for the transaction that customers buy goods from vendors. However, the customers also have some interesting goods with low price that vendors want to buy, so a bidirectional micropayment scheme with anonymous users is proposed. In our scheme, the customers not only buy goods from vendors but also sale goods to vendors in anonymous and fair way. To protect vendors’ benefits, our scheme also provides the exploring mechanism to find out who the malicious customers are. Moreover, after buying goods from anonymous customers, the vendor obtains some evidence to prove who the actual source of the bought goods is. Our scheme satisfies not only the basic security requirements of micropayment schemes but also the fairness of the sales from customers to vendors. Our simulation shows that our bidirectional scheme is practical in real life. Moreover, some security comments on two micropayment schemes for multi-merchants with anonymity and untraceability.